/*
 * Lazy Load - jQuery plugin for lazy loading images
 *
 * Copyright (c) 2007-2013 Mika Tuupola
 *
 * Licensed under the MIT license:
 *   http://www.opensource.org/licenses/mit-license.php
 *
 * Project home:
 *   http://www.appelsiini.net/projects/lazyload
 *
 * Version:  1.9.3
 *
 */

(function($, window, document, undefined) {
  var $window = $(window);

  $.fn.lazyload = function(options) {
      var elements = this;
      var $container;
      var settings = {
          threshold       : 0,
          failure_limit   : 0,
          event           : "scroll",
          effect          : "show",
          container       : window,
          data_attribute  : "original",
          skip_invisible  : true,
          appear          : null,
          load            : null,
          placeholder     : ""
      };

      function update() {
          var counter = 0;

          elements.each(function() {
              var $this = $(this);
              if (settings.skip_invisible && !$this.is(":visible")) {
                  return;
              }
              if ($.abovethetop(this, settings) ||
                  $.leftofbegin(this, settings)) {
                      /* Nothing. */
              } else if (!$.belowthefold(this, settings) &&
                  !$.rightoffold(this, settings)) {
                      $this.trigger("appear");
                      /* if we found an image we'll load, reset the counter */
                      counter = 0;
              } else {
                  if (++counter > settings.failure_limit) {
                      return false;
                  }
              }
          });

      }

      if(options) {
          /* Maintain BC for a couple of versions. */
          if (undefined !== options.failurelimit) {
              options.failure_limit = options.failurelimit;
              delete options.failurelimit;
          }
          if (undefined !== options.effectspeed) {
              options.effect_speed = options.effectspeed;
              delete options.effectspeed;
          }

          $.extend(settings, options);
      }

      /* Cache container as jQuery as object. */
      $container = (settings.container === undefined ||
                    settings.container === window) ? $window : $(settings.container);

      /* Fire one scroll event per scroll. Not one scroll event per image. */
      if (0 === settings.event.indexOf("scroll")) {
          $container.bind(settings.event, function() {
              return update();
          });
      }

      this.each(function() {
          var self = this;
          var $self = $(self);

          self.loaded = false;

          /* If no src attribute given use data:uri. */
          if ($self.attr("src") === undefined || $self.attr("src") === false) {
              if ($self.is("img")) {
                  $self.attr("src", settings.placeholder);
              }
          }

          /* When appear is triggered load original image. */
          $self.one("appear", function() {
              if (!this.loaded) {
                  if (settings.appear) {
                      var elements_left = elements.length;
                      settings.appear.call(self, elements_left, settings);
                  }
                  $("<img />")
                      .bind("load", function() {

                          var original = $self.attr("data-" + settings.data_attribute);
                          $self.hide();
                          if ($self.is("img")) {
                              $self.attr("src", original);
                          } else {
                              $self.css("background-image", "url('" + original + "')");
                          }
                          $self[settings.effect](settings.effect_speed);

                          self.loaded = true;

                          /* Remove image from array so it is not looped next time. */
                          var temp = $.grep(elements, function(element) {
                              return !element.loaded;
                          });
                          elements = $(temp);

                          if (settings.load) {
                              var elements_left = elements.length;
                              settings.load.call(self, elements_left, settings);
                          }
                      })
                      .attr("src", $self.attr("data-" + settings.data_attribute));
              }
          });

          /* When wanted event is triggered load original image */
          /* by triggering appear.                              */
          if (0 !== settings.event.indexOf("scroll")) {
              $self.bind(settings.event, function() {
                  if (!self.loaded) {
                      $self.trigger("appear");
                  }
              });
          }
      });

      /* Check if something appears when window is resized. */
      $window.bind("resize", function() {
          update();
      });

      /* With IOS5 force loading images when navigating with back button. */
      /* Non optimal workaround. */
      if ((/(?:iphone|ipod|ipad).*os 5/gi).test(navigator.appVersion)) {
          $window.bind("pageshow", function(event) {
              if (event.originalEvent && event.originalEvent.persisted) {
                  elements.each(function() {
                      $(this).trigger("appear");
                  });
              }
          });
      }

      /* Force initial check if images should appear. */
      $(document).ready(function() {
          update();
      });

      return this;
  };

  /* Convenience methods in jQuery namespace.           */
  /* Use as  $.belowthefold(element, {threshold : 100, container : window}) */

  $.belowthefold = function(element, settings) {
      var fold;

      if (settings.container === undefined || settings.container === window) {
          fold = (window.innerHeight ? window.innerHeight : $window.height()) + $window.scrollTop();
      } else {
          fold = $(settings.container).offset().top + $(settings.container).height();
      }

      return fold <= $(element).offset().top - settings.threshold;
  };

  $.rightoffold = function(element, settings) {
      var fold;

      if (settings.container === undefined || settings.container === window) {
          fold = $window.width() + $window.scrollLeft();
      } else {
          fold = $(settings.container).offset().left + $(settings.container).width();
      }

      return fold <= $(element).offset().left - settings.threshold;
  };

  $.abovethetop = function(element, settings) {
      var fold;

      if (settings.container === undefined || settings.container === window) {
          fold = $window.scrollTop();
      } else {
          fold = $(settings.container).offset().top;
      }

      return fold >= $(element).offset().top + settings.threshold  + $(element).height();
  };

  $.leftofbegin = function(element, settings) {
      var fold;

      if (settings.container === undefined || settings.container === window) {
          fold = $window.scrollLeft();
      } else {
          fold = $(settings.container).offset().left;
      }

      return fold >= $(element).offset().left + settings.threshold + $(element).width();
  };

  $.inviewport = function(element, settings) {
       return !$.rightoffold(element, settings) && !$.leftofbegin(element, settings) &&
              !$.belowthefold(element, settings) && !$.abovethetop(element, settings);
   };

  /* Custom selectors for your convenience.   */
  /* Use as $("img:below-the-fold").something() or */
  /* $("img").filter(":below-the-fold").something() which is faster */

  $.extend($.expr[":"], {
      "below-the-fold" : function(a) { return $.belowthefold(a, {threshold : 0}); },
      "above-the-top"  : function(a) { return !$.belowthefold(a, {threshold : 0}); },
      "right-of-screen": function(a) { return $.rightoffold(a, {threshold : 0}); },
      "left-of-screen" : function(a) { return !$.rightoffold(a, {threshold : 0}); },
      "in-viewport"    : function(a) { return $.inviewport(a, {threshold : 0}); },
      /* Maintain BC for couple of versions. */
      "above-the-fold" : function(a) { return !$.belowthefold(a, {threshold : 0}); },
      "right-of-fold"  : function(a) { return $.rightoffold(a, {threshold : 0}); },
      "left-of-fold"   : function(a) { return !$.rightoffold(a, {threshold : 0}); }
  });

})(jQuery, window, document);